(a) Field of the Invention
The present invention relates to a large-aperture super-telephoto lens system having the favorably corrected secondary spectrum.
(b) Description of the Prior Art
In a telephoto lens system having a long focal length, it is more difficult to correct chromatic aberration, especially the secondary spectrum, than in a lens system having a short focal length. Further, as a lens system has a longer focal length, its total length is prolonged, thereby making it more difficult to perform focusing by displacing the lens system as a whole.
For this reason, some of the conventional telephoto lens systems are so designed as to correct the secondary spectrum by using fluorite and anormally dispersive glass as materials for the front lens components through which rays transmit at their high portions. There have also been known the conventional telephoto lens systems so adapted as to perform focusing by displacing only the rear lens components having relatively small diameters. However, these conventional telephoto lens systems have small aperture ratios on the order of F/4.5 and are inconvenient in handling due to the first lens component (front lens component) made of fluorite which can easily be injured.